Ultraviolet light is a portion of the electromagnetic spectrum that has many uses. For example, ultraviolet light can be used in a purification system to kill bacteria and break down chemicals in a fluid, such as water or air. The ultraviolet radiation can converts chemicals in the water to carbon dioxide and water. If halogenated compounds are present, the ultraviolet radiation converts them into halogenated acids. Ultraviolet light can also be used in photosynthetic reactions to initiate and cause chemical reactions to make chemical compounds. These ultraviolet-light initiated reactions can take place in a gas or liquid phase. To be effective, the fluid must be exposed to ultraviolet-light radiation of a certain minimum intensity for a certain minimum time. The minimum intensity and time required for a particular process is determined by routine experimentation and analysis. Generally, the more intense the ultraviolet-light radiation, the shorter the exposure time required for a given purification or reaction objective.
As is well known in the art, an ultraviolet lamp is typically made with a straight, hollow tube of UV transparent material, typically quartz. The straight tube is sealed at both ends such that electrical connections extend through the seals into the tube. The tube is filled with a gas that is known to produce ultraviolet light when a sufficient electrical current passes through the gas.
To immerse an ultraviolet lamp in water, at least one end of the straight-tube lamp and its electrical connections are normally positioned below the surface level of the water. To protect the electrical connections of the lamp, it is normally positioned in a secondary sheath of ultraviolet transparent material. A suitable ultraviolet transparent material for the sheath is quartz, which is transparent to both ultraviolet and visible light and has some physical properties similar to glass. The quartz sheath of the reactor tube keeps water away from the lamp and its electrical connections. The ultraviolet lamp with its protective sheath is referred to herein as a reactor tube.
An ultraviolet-light reactor typically includes a tank or other chamber for holding or circulating a fluid to be treated with ultraviolet radiation. An ultraviolet reactor tube comprising the lamp and its protective quartz sheath is positioned in the reactor chamber so that fluid in the chamber is exposed to the ultraviolet radiation. Some ultraviolet-light reactors have a plurality of reactor tubes positioned in the chamber, which can provide intense ultraviolet radiation. Since the ultraviolet-light generating efficiency of a lamp gradually deteriorates with use, another purpose of the protective sheath is to allow a lamp to be periodically changed without opening the reactor chamber. In an ultraviolet-light reactor having a plurality of reactor tubes, the lamp of one reactor tube can be changed without interrupting the ultraviolet-light treatment provided by the other reactor tubes.
A problem with ultraviolet reactor tubes is that they tend to become fouled and accumulate scale. This problem is particularly acute in water treatment reactors. As fouling and scale accumulates on the outer surface of the reactor tube, it increasingly blocks the ultraviolet light from the lamp, which reduces the intensity and effectiveness of the ultraviolet-light treatment. To remove the fouling and scale, the protective sheath of the reactor tube has to be mechanically or chemically cleaned. Furthermore, the reactor tubes are often positioned in an ultraviolet-light reactor such that they are inaccessible for cleaning without at least partially dismantling the reactor. This is particularly so with a reactor that uses a plurality of reactor tubes in a chamber. For example, an ultraviolet-light reactor can have thirty reactor tubes in a single chamber. The necessary cleaning of the reactor tube to maintain the performance of the reactor has been time consuming and expensive. Thus, there has been a long-felt need for apparatus and method for cleaning the reactor tubes of an ultraviolet-light reactor.